Spherical die



Jan. 27, 1959 J. P. LIVINGSTON 2,87

SPHERICAL DIE Filed April 6, 1955 PRESSURE INVENTOR.

JACK P. LIVINGSTON Fig. 3 BY Jack 1. Livingston,

2,870,484 SP HERICAL n11;

, Los Alamos, N. Mex., assignor to the United States of America as represented by the United States Atomic Energy Commission Application April 6, 1955 Serial No. 499,711 1 Claim. (CI. 18-34) hemispherical shells have not achieved uniform density thruout the pressed shape, nor has the density desired been achieved easily and with high accuracy.

The present invention utilizes a new principle to press the powder into the die cavity without the need for relative movement between female and male die elements which leads to the desired uniform density.

An object of this invention is to provide a method and apparatus wherein either thin or thick walled hemispherical shells, hemi-elliptical shells or similar shapes may be pressed easily.

Another object of this invention is to provide a method and apparatus wherein either thin or thick walled hemispherical shells, hemi-elliptical shells or similar shapes may be pressed easily into compacts with uniform wall density.

Another object of this invention is to provide a method I and apparatus wherein either thin or thick walled hemispherical shells, hemi-elliptical shells or similar shapes may be pressed easily and with predetermined wall density.

Further objects and advantages of the present invention will be apparent from the following specifications and claim which include a preferred embodiment of the present invention, and from the drawings, hereby made a part of the specification, wherein: I

Figure 1 is a schematic view showing the pressing elements in the initial position.

Figure 2 is a graph comparing the final pressures in the pressed powder from prior art techniques and from the teachings of the present invention.

Figure 3 is a sectioned perspective showing some of the internal elements of the invention.

Figure 4 shows the powder in the final tion.

The present invention relates to dies used for hot or cold pressing of powdered metals or other powdered materials. It is particularly concerned with pressing powdered materials into hemispherical shells, hemi-ellipsoidal shells, or similar shapes.

Referring to Figure 1 of the drawing, a male forming element 10 is in a fixed position relative to a female forming element 11, and a ring 12 is freely slidable along male forming element 10. If the cavity 13 is partially filled with a powder, it can be seen that when the ring 12 is pressed posi- United States Patent 2,870,484 Patented Jan. 2-7, 1959 forced up, the hollow spherical portion of the cavity will he filledwith compacted powder, and except for small frictional losses, the Pressure thruout the powder will e c n t nt.

In the graphof Figure 2, line 14 represents the uniform pressure curve for various points in the powderas indicated in Figure 1. This curve is at a constant level or value for all points in the powder because the pressure is uniform, If the pressing were attempted by simply m vi s t e form ng elem nt 0 up n keeping the ring l2 stationary, the pressure curve would be as line 20, falling off sinusoidally to zero pressure at 0. Thus, it can be seen that the pressing apparatus of this inven tio leads to a uniform and accurately known density whereas other systems do not. In addition, it can be seen by reference to Figure 1 that the required density can be achieved by simply stopping the movement of the ring 12 at the proper time. Regardless of the position of the ring 12 when stopped, the wall of the pressed shape will be of proper thickness due to the unique design of the invention. The proper time to stop the ring is when a predetermined pressure has been reached. Naturally, the same result can be achieved by carefully measuring the amount of powder placed in cavity 13 and subsequently stopping the ring at a predetermined position, in which case every piece formed will be identical in physical size and density.

The preferred embodiment of this invention is shown as Figure 3. The die is supported on a base 17. Attached to base 17 is a vertical sleeve 15 having two diametrically opposite slots in which yoke 22 is freely slidable. Yoke 22 serves to fasten female die element 11 to male die element 10 in fixed relative position and spaced a uniform distance from each other to form cavity 13. Ring 12 is freely slidable in the cylindrical portion of cavity 13 and can be moved upward by a corresponding movement of sleeve 15. Within male die element 10 is a heating coil 21 connected to electrical power by means of leads 18 and 19. The female die section is separable at joint 16 to facilitate introduction of the pressing material and removal of the pressed piece. Locating pins 23 aid in reassembling the female die elements to exactly the same relative position. A metal ring 24 prevents material from being pressed into joint In operation, female die member 11 is separated at joint 16, and a suitable amount of powder is placed in cavity 13 above ring 12. The die element 11 is reassembled and heated by heating element 21 if a material is being pressed that forms better at an elevated temperature. Pressure is applied to the top of element 11 and the subsequent downward movement of 11 forces sleeve 15 and ring 12 to move upward in cavity 13, forcing the powder into the shaped region of cavity 13. After suitable pressure has been applied, the female die element 11 is separated at 16 and the pressed shell is removed.

The section view Figure 4 shows the powder pressed to its final shape.

It is understood that the invention as described is the preferred embodiment and that certain variations will not alter the operation or results. For example, as previously indicated, the cavity and subsequent shaped piece does not have to be the shape of a hollow hemisphere but may be a hollow hemi-ellipsoid or otherwise. The material does not have to be introduced as a powder, but may be pellets or a ring shaped to fit the cavity above the ring pusher. Furthermore, instead of heating the die elements, it is understood that they could be cooled by suitable means if desirable for the pressing operation. The female die element 11 could have a compression spring between it and base 17 so that the element 11 would always be in a raised position except when under pressure. Other appropriate changes are also understood.

a What is claimed is: a I

A die for pressing powdered materials into a hemispherical shape of uniform density and wall thickness comprising in combination a female die clement, a'male die element and a pressing ring, said female die element and said male die element held in stationary spaced relation, said space defined by said male and female elements being equivalent to said wall thickness and defining said hemispherical shape, said pressing ring linearly movable along said male die element, means for filling said space with said powdered materials, means for moving said pressing ring along said male die element whereby said powdered material is pressed into said hemispherical shape, and means for heating said male element whereby said powdered materials may be heated while simultaneously being pressed.

References Cited in the file of this patent UNITED STATES PATENTS 1,122,393 House Dec. 29, 1914 1,467,311 Elliott Sept. 11, 1923 1,658,566 McDonald Feb. 7, 1928 1,745,482 Goodwin Feb. 4, 1930 1,776,888 Clark Sept. 30, 1930 1,984,307 Keller Dec. 11, 1934 2,131,319 Greenholtz ct al. Sept. 27, 1938 2,363,808 Sayre Nov. 28, 1944 2,386,498 Ostrander Oct. 9, 1945 2,549,939 Shaw et al. Apr. 24, 1951 2,558,823 Crowley et al. July 3, 1951 Palmer Jan. 22, 1952 

